Java 루프 큐 구현

  1 public class LoopQueue {
  2 
  3     private E[] data;
  4     private int front; //  
  5     private int tail; //  
  6     private int size;
  7 
  8     public LoopQueue(int capacity) {
  9         data = (E[]) new Object[capacity + 1];
 10         front = 0;
 11         tail = 0;
 12         size = 0;
 13     }
 14 
 15     public LoopQueue() {
 16         this(10);
 17     }
 18 
 19     public int getCapacity() {
 20         return data.length - 1;
 21     }
 22 
 23     public int getSize() {
 24         return size;
 25     }
 26 
 27     public boolean isEmpty() {
 28         return front == tail;
 29     }
 30 
 31     public boolean isFull() {
 32         return (tail + 1) % data.length == front;
 33     }
 34 　　 //  
 35     public void enqueue(E e) {
 36         if (isFull()) {
 37             resize(getCapacity() * 2);
 38         }
 39         data[tail] = e;
 40         tail = (tail + 1) % data.length;
 41         size++;
 42     }
 43 
 44     private void resize(int newCapacity) {
 45         E[] newArr = (E[]) new Object[newCapacity + 1];
 46         for (int i = 0; i < size; i++) {
 47             newArr[i] = data[(front + i) % data.length];
 48         }
 49         data = newArr;
 50         front = 0;
 51         tail = size;
 52     }
 53 　　 //  
 54     public E dequeue() {
 55         if (isEmpty()) {
 56             throw new IllegalArgumentException("Cannot dequeue from an empty queue");
 57         }
 58         E res = data[front];
 59         data[front] = null;
 60         front = (front + 1) % data.length;
 61         size--;
 62         if (size == getCapacity() / 4 && getCapacity() / 2 != 0) {
 63             resize(getCapacity() / 2);
 64         }
 65         return res;
 66     }
 67 　　 
 68     public E getFront() {
 69         if (isEmpty()) {
 70             throw new IllegalArgumentException("Cannot dequeue from an empty queue");
 71         }
 72         return data[front];
 73     }
 74 
 75     @Override
 76     public String toString() {
 77         StringBuilder str = new StringBuilder();
 78         str.append(String.format("Queue: size = %d, capacity = %d
", size, getCapacity()));
 79         str.append("front [");
 80         for (int i = front; i != tail; i = (i + 1) % data.length) {
 81             str.append(data[i]);
 82             if ((i + 1) % data.length != tail) {
 83                 str.append(", ");
 84             }
 85         }
 86         str.append("] tail");
 87         return str.toString();
 88     }
 89 
 90     public static void main(String[] args) {
 91         LoopQueue queue = new LoopQueue<>();
 92         for (int i = 0; i < 10; i++) {
 93             queue.enqueue(i);
 94             System.out.println(queue);
 95             if (i % 3 == 2) {
 96                 queue.dequeue();
 97                 System.out.println(queue);
 98             }
 99         }
100     }
101 }